Hydronephrosis

What is hydronephrosis?

The term hydronephrosis is derived from the Greek words hydro for water and nephros for kidney. It refers to the enlargement of the renal pelvis and calyx system, typically caused by an accumulation of excess fluid. This condition is classified as a urinary drainage disorder.

The kidneys are paired organs located slightly below the lower ribs. They filter all the blood in the body and help remove toxic and excess substances, which are then excreted in the form of urine. To perform this important function, the kidney has a complex structure.

The renal pelvis and calyx system collect the urine and channel it into the two ureters. The fluid then travels to the bladder, from which it can be excreted as needed via the urethra. Urine flow may be obstructed for various reasons. Essentially, this causes urine to back up into the renal pelvis and dilate it.

What are the causes of hydronephrosis?

Urinary drainage disorders that lead to hydronephrosis can be either congenital or acquired later in life. Benign causes can also be distinguished from malignant ones.

The most common cause occurs in the ureter, where it can become partially or fully blocked by stones. The severity of the urinary backup depends on the degree of narrowing. This is the leading cause of hydronephrosis.

The ureter can also be narrowed due to inflammatory processes, such as those associated with tuberculosis, or congenital changes. External pressure on the ureter is also possible. In many cases, benign or malignant tumors can cause this narrowing by either compressing the ureter or growing into it.

Especially in childhood, hydronephrosis can be caused by a condition called vesicoureteral reflux. This refers to the backward flow of urine from the bladder into the ureter. It can be due to disorders of the bladder’s nerves or muscles or a urinary drainage obstruction from the bladder.

More rarely, excessive urine production can lead to the expansion of the renal pelvis and calyx system. In cases like diabetes insipidus, for example, the kidney loses its ability to concentrate the primary urine, leading to the massive excretion of highly diluted urine.

How does hydronephrosis present itself?

The symptoms of hydronephrosis can vary significantly depending on how quickly the urinary retention develops.

Gradually developing dilatations of the renal pelvis do not usually cause any symptoms in those affected. A common scenario here is narrowing of the lower ureter due to urological or gynecological tumors as well as congenital urinary retention. Patients may describe non-specific back pain or a feeling of pressure in the flank area.

On the other hand, acute urinary retention can be very painful. This is typically known as renal colic, in which very severe pain occurs in episodes. It can be explained by the fact that the ureteral muscles can no longer contract rhythmically and consequently cramp. The faster the pressure in the renal pelvis rises, the worse the pain experienced by those affected. Renal colic is typical of acute kidney stone disease.

Besides severe flank pain, additional symptoms may also occur. These include bloody urine, the absence of urine excretion or other general symptoms such as fever and chills. The latter symptoms indicate that urinary substances may already be present in the blood and that a systemic infection is developing. Rapid treatment is therefore strongly recommended.

How is hydronephrosis diagnosed?

To properly treat hydronephrosis, the exact cause of the urinary obstruction must be identified. What diagnostic measures are used therefore depend greatly the patient's symptoms because these provide important clues about the underlying cause.

The most important diagnostic tool for kidney disorders is the ultrasound, also known as sonography. This is a non-invasive and quickly available method to visualize the kidneys. During a kidney sonography, the extent of the enlargement of the renal pelvis can be assessed. In chronic cases, hydronephrosis may also be an incidental finding.

Further diagnostics may include laboratory tests or additional imaging methods. Blood tests can also help provide diagnostic clues through inflammation markers, kidney parameters, or the presence of waste substances in the blood.

A CT scan, with or without contrast, can often identify the cause of ureteral narrowing, as stones are particularly well displayed. Moreover, an excretory urography can be done. In this procedure, a contrast medium is injected through a vein, and X-rays are taken, showing the flow of urine through the contrast.

Depending on the cause of the hydronephrosis, further specialized examinations may be required. In these cases, the benefits and risks for the patient must always be weighed.

Which treatment options are available for hydronephrosis?

Urinary retention can be caused by a wide range of factors, which means that treatment ranges from conservative measures to surgical procedures.

If hydronephrosis develops acutely, the patient's pain should be treated as quickly as possible. In this case, it may be necessary to use strong painkillers to provide relief for the patient. The main objective is then to ensure adequate urine flow.

If necessary, the insertion of a ureteral stent (double-J stent) via a catheter may be required. The urine can then flow past the obstruction, and further diagnostic or therapeutic measures can be planned.

The most common cause of renal colic, stones, can be treated in different ways depending on their location and size. In the case of smaller stones, it may be sufficient to give the patient painkillers and wait for the stone to pass naturally.

Larger stones can be broken up or crushed using shockwave therapy from the outside, or they can be removed using an endoscope. Urology offers a variety of treatment options, and the appropriate method must be considered on a case-by-case basis.

If malignant tumors are the cause of hydronephrosis, not only must the urine flow be restored, but an adequate tumor therapy must also be implemented. This usually involves a combination of surgery, chemotherapy, and radiation therapy. In tumor conferences, each case is discussed individually, and a treatment plan is developed.

Can hydronephrosis be prevented?

Whether hydronephrosis can be prevented or not depends mainly on the underlying cause. Although many of the causes can hardly be influenced, the development of a stone formation can be somewhat prevented.

The formation of a urinary stone requires the urine to be supersaturated with stone-forming substances. These can include substances such as uric acid or calcium. In western societies, a diet high in salt and protein contributes to the precipitation of these substances in the form of urinary stones. Therefore, a balanced diet with little animal protein and moderate physical activity is recommended.

Furthermore, adequate fluid intake should be ensured. If the body's water balance is disturbed, the urine is usually highly concentrated to avoid excessive fluid loss. Additionally, certain medications can promote the formation of urinary stones.

In general, it is recommended to treat urinary tract infections as quickly and effectively as possible to prevent the infection from spreading to the ureters and kidneys. Certain pathogens can also alter the urine in such a way that an alkaline environment is created, which facilitates the formation of specific stones. In any case, medical attention should be sought for any issues related to the urinary tract.

Which doctors & clinics specialize in hydronephrosis?  

In many cases, the general practitioner is the first point of contact for urinary tract complaints. Simple bladder infections can be treated effectively here, but for more complex issues and detailed diagnostics, a specialist in urology should be consulted. The urologist can arrange for more in-depth diagnostics and initiate the appropriate treatment.

We want to help patients find experienced doctors for their specific complaints. Therefore, we have carefully reviewed and selected all the specialists listed here. All of our doctors are experts in urology and have extensive experience in treating hydronephrosis. See for yourself the expertise of our specialists and schedule an initial consultation.